U.S. patent application number 17/692213 was filed with the patent office on 2022-09-22 for motor controller, motor and pump device.
This patent application is currently assigned to NIDEC SANKYO CORPORATION. The applicant listed for this patent is NIDEC SANKYO CORPORATION. Invention is credited to Satoshi TANIMURA, Takashi YAMAMOTO.
Application Number | 20220302800 17/692213 |
Document ID | / |
Family ID | 1000006252678 |
Filed Date | 2022-09-22 |
United States Patent
Application |
20220302800 |
Kind Code |
A1 |
TANIMURA; Satoshi ; et
al. |
September 22, 2022 |
MOTOR CONTROLLER, MOTOR AND PUMP DEVICE
Abstract
A motor controller includes a motor control part controlling a
motor having a three-phase coil by a control signal, an inverter
applying a drive voltage supplied from a power source to the
three-phase coil based on an output signal from the motor control
part, a drive voltage line supplying the drive voltage to the
inverter, a common line electrically connected with a neutral point
of the three-phase coil, an inductor electrically connected in
series with the drive voltage line, a first capacitor between a
portion between the inverter and the inductor in the drive voltage
line and a ground, a second capacitor between a portion on an input
side with respect to the first capacitor in the drive voltage line
and the ground, and a third capacitor between the second capacitor
and the ground. The common line is electrically connected between
the second capacitor and the third capacitor.
Inventors: |
TANIMURA; Satoshi; (Nagano,
JP) ; YAMAMOTO; Takashi; (Nagano, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIDEC SANKYO CORPORATION |
Nagano |
|
JP |
|
|
Assignee: |
NIDEC SANKYO CORPORATION
Nagano
JP
|
Family ID: |
1000006252678 |
Appl. No.: |
17/692213 |
Filed: |
March 11, 2022 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K 11/33 20160101;
F04D 29/40 20130101; F04D 25/06 20130101 |
International
Class: |
H02K 11/33 20060101
H02K011/33; F04D 25/06 20060101 F04D025/06; F04D 29/40 20060101
F04D029/40 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2021 |
JP |
2021-041938 |
Claims
1. A motor controller which controls a motor having a three-phase
coil, the motor controller comprising: a motor control part which
controls rotation of the motor by a control signal; an inverter
which applies a drive voltage supplied from a driving power source
to the three-phase coil based on an output signal from the motor
control part; a drive voltage line which supplies the drive voltage
to the inverter; a common line which is electrically connected with
a neutral point of the three-phase coil; an inductor which is
electrically connected in series with the drive voltage line; a
first capacitor which is electrically connected between a portion
between the inverter and the inductor in the drive voltage line and
a ground; a second capacitor which is electrically connected
between a portion on an input side with respect to the first
capacitor in the drive voltage line and the ground; and a third
capacitor which is electrically connected between the second
capacitor and the ground; wherein the common line is electrically
connected between the second capacitor and the third capacitor.
2. The motor controller according to claim 1, wherein when a
capacitance of each of the second capacitor and the third capacitor
is defined as C1, the C1 satisfies a following conditional
expression: "0.047 .mu.F.ltoreq.C1.ltoreq.0.33 .mu.F".
3. The motor controller according to claim 1, wherein the second
capacitor is electrically connected between a portion on an input
side with respect to the inductor in the drive voltage line and the
ground.
4. The motor controller according to claim 1, wherein when a
capacitance of the first capacitor is defined as C2, the C2
satisfies a following conditional expression: "100
.mu.F.ltoreq.C2".
5. The motor controller according to claim 1, further comprising: a
control signal line configured to input the control signal into the
motor control part, and a fourth capacitor which is electrically
connected between the control signal line and the ground.
6. The motor controller according to claim 5, further comprising: a
ferrite bead which is electrically connected in series with the
control signal line in a portion on an input side with respect to
the fourth capacitor in the control signal line; and a sixth
capacitor which is electrically connected between a portion on an
input side with respect to the ferrite bead in the control signal
line and the ground.
7. The motor controller according to claim 1, further comprising:
an FG output line configured to transmit a rotation number signal
according to a rotation number of the motor to an external device;
and a fifth capacitor which is electrically connected between the
FG output line and the ground.
8. The motor controller according to claim 7, wherein when a
capacitance of the fifth capacitor is defined as C3, the C3
satisfies a following conditional expression: "C3.ltoreq.0.1
.mu.F".
9. The motor controller according to claim 3, wherein the second
capacitor is electrically connected between a portion on an input
side with respect to the inductor in the drive voltage line and the
ground.
10. The motor controller according to claim 9, wherein when a
capacitance of the first capacitor is defined as C2, the C2
satisfies a following conditional expression: "100
.mu.F.ltoreq.C2".
11. The motor controller according to claim 10, further comprising:
a control signal line configured to input the control signal into
the motor control part, and a fourth capacitor which is
electrically connected between the control signal line and the
ground.
12. The motor controller according to claim 11, further comprising:
a ferrite bead which is electrically connected in series with the
control signal line in a portion on an input side with respect to
the fourth capacitor in the control signal line; and a sixth
capacitor which is electrically connected between a portion on an
input side with respect to the ferrite bead in the control signal
line and the ground.
13. The motor controller according to claim 11, further comprising:
an FG output line configured to transmit a rotation number signal
according to a rotation number of the motor to an external device;
and a fifth capacitor which is electrically connected between the
FG output line and the ground.
14. The motor controller according to claim 13, wherein when a
capacitance of the fifth capacitor is defined as C3, the C3
satisfies a following conditional expression: "C3.ltoreq.0.1
.mu.F".
15. A motor comprising: a rotor which is rotatable with a center
axis as a center; a stator comprising a three-phase coil; and the
motor controller defined in claim 1.
16. A pump device comprising: the motor defined in claim 15; an
impeller which is fixed to the rotor; and a case which accommodates
the impeller and sections a pump chamber.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present invention claims priority under 35 U.S.C. .sctn.
119 to Japanese Application No. 2021-041938 filed Mar. 16, 2021,
the entire content of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] At least an embodiment of the present invention may relate
to a motor which is used in a pump device or the like. Further, at
least an embodiment of the present invention may relate to a motor
controller configured to control the motor.
BACKGROUND
[0003] Japanese Patent Laid-Open No. 2020-159336 (Patent Literature
1) discloses a pump device. A pump disclosed in the literature
includes a motor, an impeller fixed to a rotor of the motor, and a
case which accommodates an impeller and sections a pump chamber.
The motor includes a rotor which is turnable with a center axis as
a center, and a stator having a three-phase coil.
[0004] As a motor for the pump device, a motor provided with a
noise countermeasure may be used (see, for example, Japanese Patent
Laid-Open No. 2001-352792 (Patent Literature 2)). A motor disclosed
in Patent Literature 2 includes a control device having one
capacitor which is disposed in parallel between a neutral point of
a three-phase coil and a predetermined reference potential. Since
the control device includes the capacitor, a voltage of the neutral
point is smoothed. As a result, noise generated from the motor is
suppressed.
[0005] Recently, a pump device has been increasingly used together
with another precision apparatus and, when the pump device is used
for an application such as an on-vehicle pump, it is further
required to suppress noise generated from a motor of the pump
device. In this case, a noise countermeasure is not sufficient even
when a motor disclosed in Patent Literature 2 is used in the pump
device.
SUMMARY
[0006] At least an embodiment of the present invention may
advantageously provide a motor controller which is capable of
suppressing noise generated from a motor. Further, at least an
embodiment of the present invention may advantageously provide a
motor comprising the motor controller and a pump device comprising
the motor.
[0007] According to at least an embodiment of the present
invention, there may be provided a motor controller which controls
a motor having a three-phase coil. The motor controller includes a
motor control part which controls rotation of the motor by a
control signal, an inverter which applies a drive voltage supplied
from a driving power source to the three-phase coil based on an
output signal from the motor control part, a drive voltage line
which supplies the drive voltage to the inverter, a common line
which is electrically connected with a neutral point of the
three-phase coil, an inductor which is electrically connected in
series with the drive voltage line, a first capacitor which is
electrically connected between a portion between the inverter and
the inductor in the drive voltage line and the ground, a second
capacitor which is electrically connected between a portion on an
input side with respect to the first capacitor in the drive voltage
line and the ground, and a third capacitor which is electrically
connected between the second capacitor and the ground. In the motor
controller, the common line is electrically connected between the
second capacitor and the third capacitor.
[0008] In at least an embodiment of the present invention, the
motor controller includes an inductor which is electrically
connected in series with a drive voltage line, and a first
capacitor which is electrically connected between a portion between
an inverter and the inductor in the drive voltage line and a
ground. According to this structure, a drive voltage in the drive
voltage line can be smoothed and thus, noise generated in the drive
voltage line can be suppressed.
[0009] Further, in at least an embodiment of the present invention,
the motor controller includes a second capacitor which is
electrically connected between a portion on an input side with
respect to the first capacitor in the drive voltage line and the
ground, and a third capacitor which is electrically connected
between the second capacitor and the ground. The common line is
electrically connected between the second capacitor and the third
capacitor. According to this structure, the neutral point which is
electrically connected with the common line is clamped by the
second capacitor and the third capacitor and thus, even when a
voltage having a relatively large amplitude is generated at the
neutral point, the voltage can be smoothed. As a result, noise
generated in the motor can be suppressed.
[0010] In at least an embodiment of the present invention, when a
capacitance of each of the second capacitor and the third capacitor
is defined as C1, the C1 satisfies a following conditional
expression:
"0.047 .mu.F.ltoreq.C1.ltoreq.0.33 .mu.F".
[0011] In a case that the capacitance C1 of each of the second
capacitor and the third capacitor is smaller than 0.047 .mu.F, a
voltage of the neutral point is not sufficiently smoothed and thus,
reduction effect of the noise generated in the motor is relatively
low. Further, in a case that each capacitance C1 is larger than
0.33 .mu.F, the voltage of the neutral point is excessively
smoothed and thus, rotation characteristics of the motor are
relatively lowered. As a result, it is difficult to exhibit
excellent performance of the motor. Therefore, when the capacitance
C1 of each of the second capacitor and the third capacitor
satisfies the conditional expression of "0.047
.mu.F.ltoreq.C1.ltoreq.0.33 .mu.F", noise generated in the motor 2
can be suppressed without lowering the rotation characteristics of
the motor.
[0012] In at least an embodiment of the present invention, the
second capacitor is electrically connected between a portion on an
input side with respect to the inductor in the drive voltage line
and the ground. According to this structure, in comparison with a
case that the second capacitor is electrically connected between a
portion on an output side with respect to the inductor in the drive
voltage line and the ground, effect for suppressing noise generated
in the motor is large.
[0013] In at least an embodiment of the present invention, when a
capacitance of the first capacitor is defined as C2, the C2
satisfies a following conditional expression:
"100 .mu.F.ltoreq.C2".
[0014] In a case that the capacitance C2 of the first capacitor is
smaller than 100 .mu.F, an electric current ripple easily becomes
relatively large and a drive voltage of the drive voltage line
cannot be sufficiently smoothed. Therefore, it is difficult to
effectively suppress noise generated in the drive voltage line. On
the other hand, when the capacitance C2 of the first capacitor
satisfies the conditional expression of "100 .mu.F.ltoreq.C2",
noise generated in the drive voltage line can be suppressed.
Further, an electric current ripple is restrained and thus, the
first capacitor does not excessively generate heat. Therefore,
characteristics and reliability of the first capacitor can be
secured.
[0015] In at least an embodiment of the present invention, the
motor controller includes a control signal line configured to input
the control signal into the motor control part, and a fourth
capacitor which is electrically connected between the control
signal line and the ground. According to this structure, the
control signal transmitted through the control signal line can be
smoothed and thus, noise generated in the control signal line can
be eliminated.
[0016] In at least an embodiment of the present invention, the
motor controller includes a ferrite bead which is electrically
connected in series with the control signal line in a portion on an
input side with respect to the fourth capacitor in the control
signal line, and a sixth capacitor which is electrically connected
between a portion on an input side with respect to the ferrite bead
in the control signal line and the ground. According to this
structure, noise generated in the control signal line can be
further eliminated.
[0017] In at least an embodiment of the present invention, the
motor controller includes an FG output line configured to transmit
a rotation number signal according to a rotation number of the
motor to an external device, and a fifth capacitor which is
electrically connected between the FG output line and the ground.
According to this structure, the rotation number signal transmitted
through the FG output line can be smoothed and thus, noise
generated in the FG output line can be eliminated.
[0018] In at least an embodiment of the present invention, when a
capacitance of the fifth capacitor is defined as C3, the C3
satisfies a following conditional expression:
"C3.ltoreq.0.1 .mu.F".
[0019] In a case that a capacitance C3 of the fifth capacitor 25 is
larger than 0.1 .mu.F, although noise generated in the FG output
line can be eliminated, an output waveform of a rotation number
signal easily becomes relatively dull. Therefore, a rotation number
signal of the motor cannot be detected by an external device with a
high degree of accuracy and thus, it is difficult to control the
motor to a desired rotation number. When a capacitance C3 of the
fifth capacitor satisfies the conditional expression of
"C3.ltoreq.0.1 .mu.F", noise generated in the FG output line can be
eliminated and the motor can be controlled to a desired rotation
number.
[0020] A motor in accordance with at least an embodiment of the
present invention includes a rotor which is rotatable with a center
axis as a center, a stator having a three-phase coil, and the
above-mentioned motor controller. According to this structure,
noise generated in the motor can be suppressed.
[0021] A pump device in accordance with at least an embodiment of
the present invention includes the above-mentioned motor, an
impeller which is fixed to the rotor, and a case which accommodates
the impeller and sections a pump chamber. According to this
structure, noise generated from the pump device is suppressed and
thus, a precision apparatus used around the pump device is hard to
be affected by noise.
Effects of the Invention
[0022] According to at least an embodiment of the present
invention, a drive voltage in the drive voltage line can be
smoothed by the inductor and the first capacitor and thus, noise
generated in the drive voltage line can be suppressed. Further, the
neutral point which is electrically connected with the common line
is clamped by the second capacitor and the third capacitor and
thus, even when a voltage having a relatively large amplitude is
generated at the neutral point, the voltage can be smoothed. As a
result, the motor controller is capable of suppressing noise
generated in the motor.
[0023] Other features and advantages of the invention will be
apparent from the following detailed description, taken in
conjunction with the accompanying drawings that illustrate, by way
of example, various features of embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Embodiments will now be described, by way of example only,
with reference to the accompanying drawings which are meant to be
exemplary, not limiting, and wherein like elements are numbered
alike in several Figures, in which:
[0025] FIG. 1 is an explanatory view schematically showing a cross
section of a pump device in accordance with an embodiment of the
present invention.
[0026] FIG. 2 is a schematic circuit diagram showing a motor
controller.
[0027] FIGS. 3A, 3B and 3C are views in which capacitance of a
capacitor is compared.
DETAILED DESCRIPTION
[0028] An embodiment of the present invention will be described
below with reference to the accompanying drawings. FIG. 1 is an
explanatory view schematically showing a cross section of a pump
device in accordance with an embodiment of the present invention.
As shown in FIG. 1, a pump device 1 includes a motor 2 having a
rotor 5 which is turnable with a center axis "L" as a center, an
impeller 3 which is fixed to one side "L1" of the center axis "L"
with respect to the rotor 5, and a case 4 which accommodates the
impeller 3 and sections a pump chamber 4A. The case 4 is attached
to the motor 2 from one side "L1" with respect to the motor 2. The
pump device 1 moves fluid in an inside of the pump chamber 4A by
rotating the impeller 3 together with the rotor 5 with the center
axis "L" as a center.
[0029] The motor 2 includes the rotor 5 which is turnable with the
center axis "L" as a center, a stator 7 having a three-phase coil
6, a resin sealing member 8 which covers the stator 7, and a
circuit board 9 which is connected with the three-phase coil 6. The
motor 2 is a three-phase motor, and the three-phase coil 6 includes
a U-phase coil, a V-phase coil and a W-phase coil. A magnet is
provided on an outer peripheral face of the rotor 5.
[0030] The circuit board 9 is located on the other side "L2" with
respect to the stator 7. A motor controller 10 for controlling the
motor 2 is structured on the circuit board 9. The motor controller
10 controls rotation of the motor 2 by controlling power supply to
the three-phase coil 6.
[0031] FIG. 2 is a schematic circuit diagram showing the motor
controller 10. As shown in FIG. 2, the motor 2 controlled by the
motor controller 10 includes a U-phase coil 61, a V-phase coil 62
and a W-phase coil 63. The three-phase coil 6 is
star-connected.
[0032] The motor controller 10 includes a motor control part 11
configured to control rotation of the motor 2 by a PWM signal, an
inverter 12 configured to apply a drive voltage supplied from a
driving power source to the three-phase coil 6 based on an output
signal from the motor control part 11, a drive voltage line 13
configured to supply the drive voltage to the inverter 12, and a
common line 14 connected with a neutral point 65 of the three-phase
coil 6. The motor controller 10 includes a control signal line 15
for inputting a PWM signal from an external device into the motor
control part 11, and an FG output line 16 for transmitting a
rotation number signal according to a rotation number of the motor
2 to the external device.
[0033] The motor controller 10 includes an inductor 18, a first
capacitor 21, a second capacitor 22, a third capacitor 23, a fourth
capacitor 24, a fifth capacitor 25, a sixth capacitor 26 and a
ferrite bead 19.
[0034] The motor control part 11 is structured of an IC chip or the
like disposed on the circuit board 9. The motor control part 11
outputs an output signal for controlling the inverter 12 based on a
PWM signal inputted from the external device. Further, the motor
control part 11 outputs a rotation number signal according to a
rotation number of the rotor 5 to the external device. The external
device outputs a PWM signal to the motor control part 11 for
setting the motor 2 to a desired rotation number based on the
rotation number signal.
[0035] The inverter 12 includes switching elements Q1 and Q2
structuring upper and lower arms for the U-phase, switching
elements Q3 and Q4 structuring upper and lower arms for the
V-phase, and switching elements Q5 and Q6 structuring upper and
lower arms for the W-phase. For each of the switching elements Q1
through Q6, for example, a MOS type FET is used.
[0036] A drain of the switching element Q1, a drain of the
switching element Q3 and a drain of the switching element Q5 are
connected with the drive voltage line 13. A source of the switching
element Q2, a source of the switching element Q4 and a source of
the switching element Q6 are connected with a ground 100 through a
shunt resistor Rs. Both ends of the shunt resistor Rs are connected
with the motor control part 11 through a resistor R33 in an output
line 121 and a resistor R34 in an output line 122.
[0037] A source of the switching element Q1 and a drain of the
switching element Q2 are connected with the U-phase coil 61 of the
three-phase coil 6. A source of the switching element Q3 and a
drain of the switching element Q4 are connected with the V-phase
coil 62 of the three-phase coil 6. A source of the switching
element Q5 and a drain of the switching element Q6 are connected
with the W-phase coil 63 of the three-phase coil 6.
[0038] A capacitor 51 is connected with the source of the switching
element Q1 and the drain of the switching element Q2 on an opposite
side to a side where the U-phase coil 61 of the three-phase coil 6
is connected. A capacitor 52 is connected with the source of the
switching element Q3 and the drain of the switching element Q4 on
an opposite side to a side where the V-phase coil 62 of the
three-phase coil 6 is connected. A capacitor 53 is connected with
the source of the switching element Q5 and the drain of the
switching element Q6 on an opposite side to a side where the
W-phase coil 63 of the three-phase coil 6 is connected. The
capacitors 51 through 53 are capacitors for charging and
discharging of a bootstrap circuit.
[0039] Diodes D31 through D33 for bootstrap are respectively
connected between the capacitors 51 through 53 and the motor
control part 11. The diodes D31 through D33 are connected with the
motor control part 11 through a resistor R31.
[0040] Resistors R11 through R16 are respectively connected between
gates and sources of the respective switching elements Q1 through
Q6. Resistors R21 through R26 are respectively connected between
the gates of the respective switching elements Q1 through Q6 and
the motor control part 11. Filters 41 through 46 are respectively
connected between the drains and the sources of the respective
switching elements Q1 through Q6. Each of the filters 41 through 46
is structured of a resistor and a capacitor which are connected in
series with each other.
[0041] The inverter 12 is a circuit in which a drive voltage
supplied through the drive voltage line 13 is converted into
three-phase AC by switching the respective switching elements Q1
through Q6, and drive voltages of the three-phase AC are supplied
to the motor 2 to rotate the rotor 5 of the motor 2. The inverter
12 drives the motor 2 based on output signals outputted from the
motor control part 11.
[0042] The drive voltage line 13 supplies electric power to the
motor control part 11 and the inverter 12. In this embodiment, a
voltage of rated 12V is applied to the drive voltage line 13. An
inductor 18 and a first capacitor 21 are connected with the drive
voltage line 13. The inductor 18 is electrically connected in
series with the drive voltage line 13. The first capacitor 21 is
electrically connected between a portion between the inverter 12
and the inductor 18 in the drive voltage line 13 and the ground. In
this embodiment, a capacitance C2 of the first capacitor 21 is 150
.mu.F.
[0043] The drive voltage line 13 is connected with a capacitor 27
and a diode 31. The capacitor 27 is electrically connected between
a portion on an output side with respect to the first capacitor 21
in the drive voltage line 13 and the ground 100. The diode 31 is
electrically connected between a portion between the inductor 18
and the first capacitor 21 in the drive voltage line 13 and the
ground 100.
[0044] A first line 131 and a second line 132 are connected with
the drive voltage line 13. The first line 131 and the second line
132 are electrically connected with the motor control part 11 to
supply electric power to the motor control part 11. The first line
131 is branched on an output side with respect to the capacitor 27
and is electrically connected with the motor control part 11. The
first line 131 is connected with a capacitor 28 which is
electrically connected with the ground 100. The second line 132 is
electrically connected with the motor control part 11 through a
resistor R32.
[0045] A second capacitor 22 is connected with the drive voltage
line 13. The second capacitor 22 is electrically connected between
a portion on an input side with respect to the first capacitor 21
in the drive voltage line 13 and the ground. More specifically, the
second capacitor 22 is electrically connected between a portion on
an input side with respect to the inductor 18 in the drive voltage
line 13 and the ground. A third capacitor 23 is electrically
connected between the second capacitor 22 and the ground 100. In
other words, the second capacitor 22 and the third capacitor 23 are
connected in series between the drive voltage line 13 and the
ground 100 on an input side with respect to the inductor 18 in the
drive voltage line 13. In this embodiment, the second capacitor 22
and the third capacitor 23 are structured of the same capacitor as
each other. In other words, a capacitance C1 of the second
capacitor 22 and a capacitance C1 of the third capacitor 23 are the
same as each other. The capacitance C1 of each of the second
capacitor 22 and the third capacitor 23 is 0.1 .mu.F.
[0046] In this embodiment, a common line 14 is electrically
connected between the second capacitor 22 and the third capacitor
23. In other words, a neutral point 65 electrically connected with
the common line 14 is clamped by the second capacitor 22 and the
third capacitor 23. Further, a ground line 17 is connected between
the third capacitor 23 and the ground 100.
[0047] The control signal line 15 transmits a PWM signal from the
external device to the motor control part 11. The control signal
line 15 is connected with a ferrite bead 19, a fourth capacitor 24,
a sixth capacitor 26 and a resistor R3. The fourth capacitor 24 is
electrically connected between the control signal line 15 and the
ground 100. The ferrite bead 19 is electrically connected in series
with the control signal line 15 in a portion on an output side with
respect to the fourth capacitor 24 in the control signal line 15.
The sixth capacitor 26 is electrically connected between a portion
on an output side with respect to the ferrite bead 19 in the
control signal line 15 and the ground 100. The resistor R3 is
electrically connected in series with the control signal line 15 in
a portion on an output side with respect to the sixth capacitor 26
in the control signal line 15.
[0048] The control signal line 15 is connected with a third line
151 which is connected with the first line 131. The third line 151
is electrically connected with the control signal line 15 between
the ferrite bead 19 and the resistor R3. A resistor R2 is
electrically connected in series with the third line 151.
[0049] The FG output line 16 transmits a rotation number signal of
the motor 2 outputted from the motor control part 11 to the
external device. A fifth capacitor 25, a resistor R1 and a NOT-gate
Q7 are connected with the FG output line 16. The fifth capacitor 25
is electrically connected between the FG output line 16 and the
ground 100. The resistor R1 is electrically connected in series
with the FG output line 16 in a portion on an input side with
respect to the fifth capacitor 25 in the FG output line 16. The
NOT-gate Q7 is electrically connected in series with the FG output
line 16 in a portion on an input side with respect to the resistor
R1 in the FG output line 16. In this embodiment, a capacitance C3
of the fifth capacitor 25 is 0.047 .mu.F.
(Operations and Effects)
[0050] The motor controller 10 in this embodiment includes the
inductor 18, which is electrically connected in series with the
drive voltage line 13, and the first capacitor 21 which is
electrically connected between a portion in the drive voltage line
13 between the inverter 12 and the inductor 18 and the ground 100.
According to this structure, a drive voltage in the drive voltage
line 13 can be smoothed and thus, noise generated in the drive
voltage line 13 can be suppressed.
[0051] Further, the motor controller 10 in this embodiment includes
the second capacitor 22, which is electrically connected between a
portion on an input side with respect to the first capacitor 21 in
the drive voltage line 13 and the ground 100, and the third
capacitor 23 which is electrically connected between the second
capacitor 22 and the ground 100. The common line 14 is electrically
connected between the second capacitor 22 and the third capacitor
23. Therefore, the neutral point 65 which is electrically connected
with the common line 14 is clamped by the second capacitor 22 and
the third capacitor 23 and thus, even when a voltage having a
relatively large amplitude is generated at the neutral point 65,
the voltage can be smoothed. As a result, noise generated in the
motor 2 can be suppressed. Further, the second capacitor 22 is
electrically connected between a portion on an input side with
respect to the inductor 18 in the drive voltage line 13 and the
ground 100 and thus, in comparison with a case that the second
capacitor 22 is electrically connected between a portion on an
output side with respect to the inductor 18 in the drive voltage
line 13 and the ground 100, effect for suppressing noise generated
in the motor 2 is large.
[0052] The motor controller 10 in this embodiment includes the
control signal line 15 for inputting a PWM signal from an external
device into the motor control part 11, and the fourth capacitor 24
which is electrically connected between the control signal line 15
and the ground 100. Therefore, the PWM signal transmitted through
the control signal line 15 can be smoothed and thus, noise
generated in the control signal line 15 can be eliminated. In
addition, the motor controller 10 in this embodiment includes, in a
portion on an output side with respect to the fourth capacitor 24
in the control signal line 15, the ferrite bead 19 which is
electrically connected in series with the control signal line 15,
and the sixth capacitor 26 which is electrically connected between
a portion on the output side with respect to the ferrite bead 19 in
the control signal line 15 and the ground 100. According to this
structure, noise generated in the control signal line 15 can be
further eliminated.
[0053] The motor controller 10 in this embodiment includes the FG
output line 16 for transmitting a rotation number signal according
to a rotation number of the motor 2 to an external device, and the
fifth capacitor 25 which is electrically connected between the FG
output line 16 and the ground 100. Therefore, the rotation number
signal transmitted through the FG output line 16 can be smoothed
and thus, noise generated in the FG output line 16 can be
eliminated.
[0054] Next, capacitances of the first capacitor 21, the second
capacitor 22, the third capacitor 23 and the fifth capacitor 25
will be explained below. FIGS. 3A, 3B and 3C are views in which
capacitance of a capacitor is compared.
[0055] As shown in FIG. 3A, in a case that a capacitance C2 of the
first capacitor 21 is smaller than 100 .mu.F, an electric current
ripple easily becomes relatively large and a drive voltage applied
to the drive voltage line 13 cannot be sufficiently smoothed.
Therefore, it is difficult to effectively suppress noise generated
in the drive voltage line 13. In this embodiment, the capacitance
C2 of the first capacitor 21 is 150 .mu.F and satisfies "100
.mu.F.ltoreq.C2" and thus, noise generated in the drive voltage
line 13 can be suppressed. Further, an electric current ripple is
restrained and thus, the first capacitor 21 does not excessively
generate heat. Therefore, characteristics and reliability of the
first capacitor 21 can be secured.
[0056] As shown in FIG. 3B, in a case that the capacitance C1 of
each of the second capacitor 22 and the third capacitor 23 is
smaller than 0.047 .mu.F, a voltage of the neutral point is not
sufficiently smoothed and thus, reduction effect of the noise
generated in the motor 2 is relatively low. Further, in a case that
each capacitance C1 is larger than 0.33 .mu.F, the voltage of the
neutral point is excessively smoothed and thus, rotation
characteristics of the motor 2 are relatively lowered. As a result,
it becomes difficult to exhibit excellent performance of the motor
2. Therefore, in this embodiment, the capacitance C1 of each of the
second capacitor 22 and the third capacitor 23 is 0.1 .mu.F and
satisfies "0.047 .mu.F.ltoreq.C1.ltoreq.0.33 .mu.F" and thus, noise
generated in the motor 2 can be suppressed without lowering
rotation characteristics of the motor 2.
[0057] As shown in FIG. 3C, in a case that a capacitance C3 of the
fifth capacitor 25 is larger than 0.1 .mu.F, although noise
generated in the FG output line 16 can be eliminated, an output
waveform of a rotation number signal easily becomes relatively
dull. Therefore, a rotation number signal of the motor 2 cannot be
detected by an external device with a high degree of accuracy and
thus, it is difficult to control the motor 2 to a desired rotation
number. Accordingly, in this embodiment, a capacitance C3 of the
fifth capacitor 25 is 0.047 .mu.F and satisfies "C3.ltoreq.0.1
.mu.F" and thus, noise generated in the FG output line 16 can be
eliminated and the motor 2 can be controlled to a desired rotation
number.
[0058] The motor 2 in this embodiment includes the above-mentioned
motor controller 10 and thus, noise generated in the motor 2 is
suppressed. As a result, in a case that the motor 2 in this
embodiment is used in the pump device 1, noise generated from the
pump device 1 is suppressed and thus, a precision apparatus used
around the pump device 1 is hard to be affected by noise. In the
embodiment described above, the motor 2 is used in the pump device
1, but the motor 2 may be used in various applications.
[0059] While the description above refers to particular embodiments
of the present invention, it will be understood that many
modifications may be made without departing from the spirit
thereof. The accompanying claims are intended to cover such
modifications as would fall within the true scope and spirit of the
present invention.
[0060] The presently disclosed embodiments are therefore to be
considered in all respects as illustrative and not restrictive, the
scope of the invention being indicated by the appended claims,
rather than the foregoing description, and all changes which come
within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein.
* * * * *